Closure for a pyrotechnic unit

ABSTRACT

A closure for a pyrotechnic unit ensures that upon the build-up of pressure of a pyrotechnic charge ( 24 ) no pieces which fly off occur. That is achieved in that the cover ( 4 ) has a desired-rupture location ( 32 ) in the form of a circular ring, except for a portion ( 14 ), wherein the residual cover ( 36 ) which tears open is non-detachably connected to the cover ( 4 ).

[0001] The invention relates to a closure for a pyrotechnic unit, as set forth in the classifying portion of claim 1.

[0002] In an alarm or warning light unit or flare, which is not a prior publication, a case with a pyrotechnic charge is closed by a cover of steel, which is pressed into the case. A firing device for the pyrotechnic charge is centrally fixed in the cover. In use, upon firing of the alarm or warning light unit, the cover is thrown off by the pressure which is produced. In many cases personal injuries were caused by covers flying off.

[0003] Therefore the object of the invention is to propose a closure for a pyrotechnic unit, in which in an operational situation there are no pieces which fly off.

[0004] The invention attains that object in accordance with the characterising features of claim 1. Advantageous developments of the invention are to be found in the appendant claims.

[0005] In accordance with the invention, when a pressure builds up in the interior of the pyrotechnic unit, the cover tears open along its desired-rupture location, with the tearing-open effect beginning partially opposite an angular portion acting as a hinge. As a result, there is already a reduction in pressure by virtue of the cover partially tearing open and by virtue of the further tearing-open effect, in the millisecond range, as far as the angular portion, so that a maximum possible gas pressure is certain to be avoided.

[0006] The angular portion is distinguished in that it does not have a desired-rupture location.

[0007] An embodiment of the invention is illustrated in the drawing in which:

[0008]FIG. 1 is a view from above of a cover,

[0009]FIG. 2 shows the cover of FIG. 1 in cross-section on line II-II, and

[0010]FIG. 3 is a view on an enlarged scale of the portion III in FIG. 2.

[0011] Referring to FIGS. 1 and 2, a cover 4 provided with an inward recess 2 has an outer collar or flange 6 and, on the cover side, an outer ring 8.

[0012] A wedge-shaped stamping 12 is provided in the ring 8 at the inside 10 of the cover. The stamping 12 extends in the form of a circular ring, more specifically except for a portion 14. That portion 14 is free of the stamping 12, in other words, there the continuous cross-section of the cover, that is to say the thickness 16 of the cover, is present there.

[0013] A firing device 20 is fixed in a central bore 18.

[0014] The cover 4 fits over a case shown in dash-dotted line, with a pyrotechnic charge 24 which is also shown in dash-dotted line. The cover 4 is glued to the case 22.

[0015] The thickness 16 of the cover is 1 millimeter. In the region of the stamping 12, 0.1 millimeter remains as the residual thickness 26. A wedge angle 28 is 20°.

[0016] After firing of the pyrotechnic charge 24, a pressure builds up in the interior 30 of the case 22 closed by the cover 4. At a suitable critical gas pressure, the residual thickness 26 tears in the region of the greatest stress at the desired-rupture location 32 afforded by the stamping, more specifically opposite the portion 14 in the region of the point 34. In accordance with the material stresses caused by the pressure at the desired-rupture location 32, the residual thickness 26 tears open continuously along the desired-rupture location 32, so that only the portion 14 remains. Concomitantly with the desired-rupture location 32 tearing open, the residual cover 36 indicated in dash-dotted line pivots upwardly in the direction indicated by the arrow 38, as a result of the gas pressure.

[0017] Therefore, no parts which fly off and which could result in personal injury occur during the opening procedure. 

1. A closure for a pyrotechnic unit in which a case (22) is closed with a cover (4) with a collar (6), wherein after firing of a pyrotechnic charge (24) in the case (22) the internal pressure causes opening at the cover part, characterised in that the cover (4) has a desired-rupture location (32) in the form of a circular ring, except for a portion (14), wherein the residual cover (36) which tears open is non-detachably connected to the cover (4).
 2. A closure according to claim 1 characterised in that the desired-rupture location (32) is near the collar (6).
 3. A closure according to claim 1 characterised in that the portion (14) is 5-60°.
 4. A closure according to claim 1 characterised in that the cover (4) is glued to the case (22) in the region of its collar (6).
 5. A closure according to claim 4 characterised in that the collar (6) bears externally against the case (22).
 6. A closure according to claim 1 characterised in that the cover (4) comprises aluminium and has a stamping (12) at its inside (10).
 7. A closure according to claim 6 characterised in that the cover (4) is of a thickness of from 0.6 to 1.8 millimeter and the residual thickness (26) in the region of the stamping is from 0.1 to 0.3 millimeter. 